In masonry components strengthened with externally bonded composites, good bonding is one of the most important aspects governing structural behavior, since failure usually takes place with detachment between reinforcement and substrate. This type of event is a brittle, sudden and therefore undesirable failure mechanism; nor does it allow the full strength of the reinforcement to be exploited. Many experimental data on bonding have recently become available from a Round Robin Test carried out within the framework of RILEM TC-223. In the present paper, experimental tests were simulated at increasing levels of complexity; bond behavior was first studied with an analytical model based on bi-linear representation of bond law. Two-dimensional and three-dimensional finite element analyses were then performed, according to various bond-slip laws. In particular, a number of bi-linear and non-linear interface laws were used, calibrated according to several strategies but with the same experimental population. Lastly, several commercial codes and types of finite elements were examined. This work may be said to represent a numerical Round Robin Test, with various simulations and modeling approaches. Analytical and numerical results are compared with experimental ones, in terms of both overall behavior (load to displacement curve) and local behavior (strain profiles on reinforcements at increasing load values), showing the importance of both types of information in order to obtain reliable predictions of experimental results
In this paper, the structural behavior of masonry panels strengthened with a system made up of composite fiber grids embedded in a cementitious matrix (FRCM) is presented. The non-linear behavior of the unreinforced and reinforced panels is numerically simulated by means of a simplified micro-modelling approach. This approach concentrates all the non-linearities and failures in the joints and in potential crack surfaces within the bricks, placed vertically in the middle of each brick. The FRCM strengthening system is discretized by a continuous bi-directional fiber grid constituted by trusses embedded into a cementitious matrix. A calibrated bond-slip relationship is applied between the fibers and the mortar matrix assuming an idealized bilinear law. The typical experimental load–displacement curve for a FRCM strengthened panel shows three principal phases that correspond to different failure mechanisms: masonry cracking, mortar matrix cracking and ultimate failure of the panel. The non-linear numerical analyses show a good agreement with experimental results and the modeling approach is found to be adequate to reproduce the described experimental behavior. The results of a parametric study on both the material and the geometrical properties of the FRCM system are also presented.
In the present paper, structural behaviour of masonry columns strengthened with fiber reinforced cementitious matrix have been investigated; in particular, numerical 3D simulations calibrated on experimental tests have been presented. T hree-dimensional numerical model, realized by using the commercial code MIDAS FEA, based on a macro-model approach, has been used to simulate the nonlinear structural behavior of masonry columns strengthened with FRCM, and two different models for unreinforced and strengthened columns have been adopted. The 3D numerical approach are presented and results discussed to investigate the interaction between masonry columns and reinforcement. The numerical model has been calibrated on a large number of experimental tests on confined masonry columns carried out at the University of Bologna; in particular, columns have been wrapped by FRP and FRCM and with different arrangements (continuous and discontinuous). The comparison of the numerical models with the experimental outcomes shows a good matching in terms of axial forces-strain curves and strength peak.
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